When we picked up our Timber Ridge, I put a new chrome ball on the new hitch head before delivery. Lubed, always is. Got home with trailer, unhitched, went to clean grease off of ball. Chrome all galled up, ball gouged. Dlr replaced with same ball, no refund!! Still in garage unused! I purchased and installed a new raw steel ball, and same thing on first trip out. Gouged and scored. Funny thing was that it was on the back of ball just down from the flat spot.
Never had looked into coupler till hit in face twice!! Found a fairly good sized gouge and metal piled up on itself. After carefully grinding out the scab of metal and smoothing as much as possible, next new raw ball has shown no extreme or abnormal wear in 3000 miles of towing.
My thoughts were that: 1 - chrome galled off 1st ball, then the junk in the coupler did in the next ball. 2 - Transporter with "very" used balls (!!) and no lube caused the orig damage on delivery to dealer. No way to really tell which it may have been.
Dealer wanted to replace coupler assy, but I felt I didn't want a brand new trailer to go under the torch and welding wire. They documented problem for future reference in necc. As mentioned, no further wear seen.
Check your coupler inside, and, in my opinion, get rid of the chrome ball and go to a good raw steel ball. You probably have as much tongue weight as I do, in the 1100-1200# range loaded. I really don't believe a chrome ball should be used in that range.